There are two main classes of 3D auto-stereoscopic displays that based on using different approaches: “space multiplexing (sharing)” or and “time sequencing (sharing)”.
The main disadvantage of 3D auto-stereoscopic displays using space sharing approach is that the resolution of the 3D image is reduced with increasing the number of perspective views forming the 3D image in the field of view. That results in 3D image quality degradation and restriction of its viewing angle.
Unlike space-sharing displays, 3D auto-stereoscopic time-sequencing display systems reproduce 3D image with resolution that doesn't depend on the number of perspective views. That allows widening the 3D image viewing angle by increasing the number of perspective views without reducing resolution of the 3D image.
There are several 3D projection display systems known in the prior art that embody the time-sequencing approach and use at least two lens matrices (arrays), for example, the ones described in U.S. Pat. No. 7,944,465 B2, and U.S. Pat. No. 8,243,127 B2 and US Patent Application US 2005/0270645.
US Patent Application US 2005/0270645 describes a 3D display apparatus comprising a display component for generating a sequence of 2-dimensional (2D) images and an image scanning assembly consisting of a first lens matrix (array), a second lens matrix (array) optically coupled to the first lens matrix (array) via intermediary optical assembly.
The peculiarity of this scanning assembly consists in that the first lens array can be made significantly smaller than the second array, if the intermediary optical assembly is a magnification system. This allows shifting the first lens array for scanning images instead of shifting the second array that can be made much larger and thereby significantly reduce the mechanical complexity of the scanning operation and make 3D display systems more compact. This is much more favorable for 3D display systems with the large screen.
However, this advantage is achieved at the expense of increasing optical cross-talk. There are two sources of cross-talk in the image scanning assembly described in US Patent Application US 2005/0270645. One of them (the first source) is associated with shifting the structure of optical beams at the second lens array (shown FIG. 1, Prior Art) relative to the structure of the second lens array during the scanning operation. The second source of cross-talk is associated with the mismatch between the structure of 2D images at the first lens array shifting during the scanning operation and the structure of this array.
It is worth noting that the level of cross-talk from both sources grows with the amplitude of the displacement of the first lens array, resulting in 3D image quality degradation and restriction of its viewing angle.
It should be noted that the second source of cross-talks could be eliminated if the first lens array is displaced together with the display component. But in this case, higher mechanical complexity can effectively cancel the advantage of using a small-size first lens array. Therefore, it is necessary to find another decision to solve this cross-talk problem.
The said crosstalk problems can be partially solved by adopting the solution describing the 3D display systems disclosed in the prior art (U.S. Pat. No. 7,944,465 B2 and U.S. Pat. No. 8,243,127 B2). Each of these systems comprises a display component for generating a sequence of 2-dimensional (2D) images, an image scanning assembly consisting of a first lens matrix (array) and a complex of two (second and third) lens matrices (arrays), and a mechanism for transverse displacement of the first matrix or the complex of matrices relative to each other to provide the scanning operation.
Actually, due to the use of three lens arrays, the level of cross-talk related to the said first source of cross-talk is significantly reduced, thereby allowing better quality of the 3D image and a larger viewing angle. This is provided by the fact that during the scanning operation an optical beam going through each lens of the second lens array is directed by the said lens to the respective lens of the third lens array within the aperture of the latter lens.
Meanwhile, the said second source of cross-talk is inherent both in 3D display systems disclosed in the respective versions of U.S. Pat. No. 7,944,465 B2 and U.S. Pat. No. 8,243,127 B2 associated with the movement of the first matrix and in those of US 2005/0270645. That prevents from further increasing quality of the 3D image and its viewing angle.
Besides, the possibility of using the solution disclosed in U.S. Pat. No. 7,944,465 B2 and U.S. Pat. No. 8,243,127 B2 for implementation of large-screen 3D display systems is restricted because of higher mechanical complexity of the scanning operation.
It should be noted that implementation of large-screen 3D display systems based on both the solution disclosed in U.S. Pat. No. 7,944,465 B2 and U.S. Pat. No. 8,243,127 B2 and the solution disclosed in US 2005/0270645 is not feasible without reducing the level of cross-talk mentioned above.
Therefore, it is necessary to find another solution for implementation of large-screen 3D display systems to solve prior art problems related to cross-talk and mechanical complexity of the scanning operation.
This conclusion is equally applicable both to rear-projection autostereoscopic 3D display systems and to front-projection autostereoscopic 3D display systems. Meanwhile, these 3D display systems have different fields of application. Thus, front-projection autostereoscopic 3D display systems are preferably used when the screen of a very large size (in particular, jumbo screen) is required.